Power transmission



Nov. 9, 1965 D. G. SNOW ETAL 3,216,363

POWER TRANSMISSION Filed April 24, 1965 I Ql 66 36 46 52 48 4O 74 02 FIG. 4

FIG. 3

INVENTORS DOUGLAS G. SNOW BY ROY R. STARKE United States Patent 3,216,363 POWER TRANSMISSION Douglas G. Snow, Walled Lake, Mich., and Roy R. Starke, Palm Beach Garden, Fla., assignors to Sperry Rand Corporation, Troy, Mich., a corporation of Delaware Filed Apr. 24, 1963, Ser. No. 275,438 13 Claims. (Cl. 103136) This invention relates to power transmissions, and is particularly applicable to those of the type comprising two or more fluid pressure energy translating devices, one of which may function as a pump and another as a fluid motor.

More particularly, the invention relates to a rotary vane pumping unit of the double throw type wherein vanes slidably mounted in slots of a rotor rotatably mounted within a vane track having two inlet ramps and two outlet ramps are extended and retracted twice during each rotation of the rotor.

With the rotor mounted within a vane track of the type mentioned, two diametrically opposed pumping chambers are formed between the periphery of the rotor and the vane track, each chamber comprising a fluid inlet zone and a fluid outlet zone through which the outer ends of the vanes pass as the rotor turns. Normally, the vane track is formed so that each vane does not partake of any substantial radial movement through what is known as a major dwell between the inlet and outlet ramps of the same pumping chamber and also during a minor dwell between the outlet ramp of one pumping chamber and the inlet ramp of the other pumping chamber.

Fluid supply is adapted to be conducted to the fluid inlet zones and displacement conducted from the fluid outlet zones respectively by means of branched inlet and outlet passages, the branches of which conventionally terminate in arcuate ports registering with the fluid inlet and outlet zones and which may be located in a plane wall of the housing or in a cheek plate of either the fixed or pressure loaded type. Vane pumps of the type mentioned are disclosed in the patent to Harry F. Vickers, No. 1,989,900, and the patent to Duncan B. Gardiner, No. 2,544,988, the former of which is of the mechanically clamped fixed cheek plate type and the latter of which incorporate sa cheek plate of the pressure loaded type.

In such devices, the use of springs for initially and continuously maintaining the vanes in engagement with the track has been avoided. On starting the pump, centrifugal force is depended upon to throw the vanes outwardly in their slots into engagement with the track and subsequently upon generation of flow and build up of system pressure to continuously maintain engagement with the track .by the medium of connecting the outlet side of the device to inner pressure elfective surfaces of the vanes. This may be done by connecting the outlet passage to a continuous circular groove registering with enlarged porting at the inner end of each vane slot so as to expose the inner ends of said vanes to outlet pressure, such as disclosed in the aforementioned patents to Harry F. Vickers and Duncan B. Gardiner, Nos. 1,989,900 and 2,544,988, or by the use of well-known interrupted porting, i.e., separate under-vane ports for the inner ends of vanes traversing each ramp of the device. Although pumps of this general type have proved to be very satisfactory particularly in the machine tool and mobile equipment field, a problem has been encountered in special applications where the pump is required to generate flow at extremely low starting rpm. and temperatures.

The erratic starting or generation of flow by such pumps under the extreme conditions mentioned is caused by the inability of the vanes to track simultaneously through the major dwell of both pumping chambers, thus resulting in short-oircuiting of the fluid. Without simultaneous tracking of the vanes in both pumping chambers, fluid displaced through the fluid outlet zone of one pumping chamber short-circuits back to the inlet through the other pumping chamber in which the vanes are not tracking across the major dwell of such chamber. This results in failure to build up system pressure which is depended upon to induce proper vane tracking action.

It is, therefore, an object of this invention to provide an improved rotary vane pump of the double throw type.

It is another object of this invention to provide a rotary vane pump of the double throw type having an improved vane tracking arrangement.

It is still another object of this invention to provide a rotary vane pump of the double throw type capable of consistently generating flow at low starting speeds and temperatures.

It is still another object of this invention to provide in a rotary vane pump incorporating a vane track having two inlet ramps and two outlet ramps having dwell portions therebetween, and wherein tracking of the vanes across the dwell portions between the inlet and outlet ramps is essential; for building up of system pressure which in turn is utilized for inducing proper vane action, an arrangement forinterrupt-ing connection of the fluid outlet zones with the outlet passage and cross-connecting the fluid outlet zones independently to pressure effective surfaces of vanes passing through the fluid inlet zones of opposite pumping chambers to assure proper vane tracking across the dwell portions of the device.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing wherein a preferred form of the present invention is clearly shown.

In the drawing:

FIGURE 1 is a longitudinal section through pumping mechanism embodying the present invention and taken on line 1-1 of FIGURE 3.

FIGURE 2 is a section taken on line 22 of FIG- URE 1.

FIGURE 3 is a section taken on a line 3-3 of FIG- URE 1.

FIGURE 4 is a schematic drawing illustrating the hydraulic circuitry of the present invention.

Referring now to FIGURES 1 and 2, there is shown a rotary vane pump indicated generally by the numeral 10 comprising a housing 12 having a cavity 14 closed at one end thereof :by an end cap closure member 16 and having mounted within the cavity a pumping cartridge comprising a vane carrying rotor 18 telescopically mounted within a cam ring or vane track member 20 which are sandwiched between a cheek plate 22 and a pressure loaded cheek plate 24. The rotor 18 is supported on and driven by a shaft 25, which is rotatably supported in bearings 27 and 29 respectively in the housing 12 and end cover 16.

As shown more clearly in FIGURE 3, the rotor is constructed with a plurality of substantially radial vane slots 26 each of which has a flat rectangular shaped vane 28 slidably mounted therein, each vane having an outer surface 30 adapted to engage an inner surface of the cam ring member 20, the inner generally elliptical surface of which forms a vane track indicated generally by the numeral 32.

The track 32 which surrounds rotor 18 and vanes 28 includes a pair of diametrically opposed inlet ramps 34 and 36 across which the vanes move outward as the rotor turns, and a pair of diametrically opposed outlet ramps 38 and 40 which urge the vanes inward. Two diametrically opposed pumping chambers are formed between the periphery of the rotor and the vane track through which the outer ends of the vanes pass as the rotor turns, one of said chambers indicated generally by the numeral 41 comprising a fluid inlet zone 42 and a fluid outlet zone 44 respectively correlated with the inlet ramp 34 and outlet ramp 38 and the other pumping chamber indicated generally by the numeral 45 comprising a fluid inlet zone 46 and a fluid outlet zone 48 respectively correlated with inlet ramp 36 and outlet ramp 40.

As each vane crosses over between the inlet ramp and the outlet ramp of the same pumpingchamber it partakes of substantially no radial movement during what is called a major dwell, the major dwell of the vane track between inlet ramp 34 and outlet ramp- 38 of pumping chamber 41 being indicated by the numeral 50 and the major dwell between inlet and outlet ramps 36 and 40 of pumping chamber 45 being indicated by the numeral 52. As the vanes cross over from the outlet ramp of one pumping chamber to the inlet ramp of the next pumping chamber, it again partakes of substantially no radial movement during what is called a minor dwell, the minor dwell between outlet ramp 38 of one pumping chamber 41 and inlet ramp 36 of the succeeding pumping chamber 45 being indicated by the numeral 54 and the minor dwell between outlet ramp 40 of pumping chamber 45 and inlet ramp 34 of the succeeding pumping chamber 41 being indicated by the numeral 56.

For the purpose of connecting a fluid supply to the fluid inlet zones of the pump, the housing 12 is provided with an inlet port 58, shown in FIGURE 3, which is connected by cored branched inlet passages 60 and 62 to a pair of diametrically opposed slotted inlet ports in each cheek plate which extend from the periphery of each cheek plate inwardly and which open at their interior faces adjoining the vane track and rotor to register with the fluid inlet zones. The diametrically opposed fluid inlet ports in the pressure loaded cheek plate 24 respectively connected to branch inlet passages 60 and 62 are indicated in FIGURE 2 by the numerals 64 and 66 and those located in cheek plate 22, shown in FIGURE 3, respectively axially opposed to ports 64 and 66 are indicated by the numerals 68 and 69. The axially opposed slotted inlet .ports in the cheek plates 22 and 24 are interconnected for the purpose of balanced inlet feeding by slots in the outer periphery of the cam ring or track member 20 which are shown in FIGURE 3 indicated by the numerals 70 and 71. 'Inlet ports 64 and 68 in cheek plates 22 and 24 open to and register with fluid inlet zone 42 while inlet ports 66 and 69 in said cheek plates open to and register with fluid inlet zone 46.

Although, at starting, fluid displacement from the fluid outlet zones is temporarily closed from communication with an outlet port 72 in housing 12 by an arrangement hereinafter explained, when the vanes of both pumping chambers are properly tracking fluid displacement from the fluid outlet zones 48 and 44 is conducted to the outlet port 72 of housing 12 through the medium of diametrically opposed outlet ports 74 and 76 which extend completely through the cheek plate 24. Outlet ports 74 and 76 register respectively with fl'uild outlet zones 48 and 44 of pumping chambers 45 and 41 and open on the opposite outer face of the cheek plate to an outlet chamber 78 which is directly connected to the outlet port 72. Mirror images of the outlet ports 74 and 76 in cheek plate 24 are formed in the cheek plate 22, as shown in FIGURE 3, one of which is axially opposed to outlet port 74 and indicated by the numeral 80 and the other opposed to outlet port 76 is indicated by the numeral 81. The two pairs of axially opposed outlet ports in cheek plates 22 and 24 are cross-connected by appropriate slots in the ring,.shown in FIG- URE 3, and indicated by the numerals 82 and 83.

For the purpose of aidi g centrifugal force in extending the vanes in their slots and for maintaining the outer tips of the vanes in engagement with the vane track, the cheek plates are provided with under-vane porting of the interrupted type to which pressure fluid is conducted and which register with enlarged vane slots ports 84 at the inner end of each vane slot as the rotor turns. Thus, as shown in FIGURE 2, the cheek plate 24 is provided with diametrically opposed under-vane ports 86 and 88 which are located radially inward of inlet ports 64 and 66 so as to register with the vane slot ports 84 of those vanes respectively passing through inlet zone 42 while crossing over inlet ramp 34 and with the vane slot ports of those vanes passing through inlet zone 46 while crossing over inlet ramp 36.

Each vane has an inner pressure effective surface 90 exposed to pressure transmitted to the inner end of the vane slots through the enlarged vane slot ports 84. Cheek plate 24 is also provided with diametrically opposed under-vane ports 92 and 94 radially inward of fluid outlet ports 74 and 76 which are adapted to register with the vane slot ports 84 of those vanes respectively passing through the fluid outlet zones 48 and 44. For the purpose of pressure balancing the extreme inner and outer surfaces of those vanes passing through the fluid outlet zones 48 and 44, the fluid outlet ports 74 and 76 in cheek plate 24 are respectively directly connected by passages 96 and 98 in the cheek plate 24 to the diametrically opposed under-vane ports 92 and 94.

Cheek plate 22 is provided with four under-vane ports which are mirror images of those in cheek plate 24 and which are shown in FIGURE 3 in dotted lines, undervane ports 87 and 89 being mirror images of under-vane ports 86 and 88 of check plate 24 and under-vane ports 93 and being mirror images of under-vane ports 92 and 94 of check plate 24. The cheek plate 22 is also provided with passages which interconnect the mirror image IOlltiGt ports in such cheek plate to their respective under-vane ports in the rotor which are shown in dotted lines in FIGURE 3, the passage indicated by the numeral 99 connecting outlet port 80 of that plate 'to under-vane port 93 and the passage indicated by the numeral 101 connecting outlet port 81 to under-vane port 95.

The pump device so far described with the exception of connecting the cheek plate outlet ports directly to correlated under-vane porting is that of a conventional rotary vane device of the double throw type. In such conventional devices, the outlet passage of the device comprising outlet chamber 78 would be directly connected to either a continuous circular pressure groove registering with all of the enlarged under-vane slot ports, or when interrupted porting is utilized as in the present device would be continuously connected to the under-vane ports of those vanes passing through the fluid inlet zones and of those vanes passing through the fluid outlet zones. In such conventional devices, as the fluid outlet zones are connected to the outlet passage and to each other by means of branched parallel circuitry, if on starting, the vanes which are induced outwardly only by centrifugal force do not track simultaneously through the major dwells of both pumping chambers, fluid pumped from the outlet zone of the pumping chamber within which the vanes are tracking properly is short-circuited through the parallel circuitry, to the inlet of the pumping chamber within which the vanes are not tracking. Thus, system pressure can not be built up which is depended upon to induce and maintain proper vane action.

The present invention provides an arrangement wherein, if at pump starting, proper vane action takes place through the major dwell of only one pumping chamber, proper vane tracking through the major dwell of the other pumping chamber is assured. Means are provided wherein parallel connection of the fluid outlet zones to the outlet passage and to each other is temporarily interrupted by closing communication between each fluid outlet zone and its correlated branch passage with the outlet passage and with each other, and at the same time cross-connecting the fluid outlet zone of one pumping chamber 41 to the undervane porting of those vanes passing through the fluid inlet zone of the other pumping chamber 45 and cross-connecting the fluid outlet zone of pumping chamber 45 to the under-vane porting of those vanes passing through the fluid inlet zone of pumping chamber 41.

Referring to FIGURE 1, a perforated valve disc member 102 is slidably mounted in outlet chamber 78, the outer peripheral surface 104 of which engages the cylindrical wall surface of cavity 14 within outlet chamber 78. The valve disc member 102 is resiliently :biased -by a spring 106 so that the inner plane surface 108 of the disc engages an outer flange surface 110 of check plate 24 facing the chamber 78, the fluid outlet ports 74 and 76 of the plate 24 opening to said outer flange surface. Cheek plate 24 is provided with a hub 112 so as to form the flange, the hub being slidably mounted in a stepped portion 114 of cavity 14. The centrally located perforation of disc member 102 indicated by the numeral 116 is proportioned to leave a spacing for fluid flow around the hub portion of the cheek plate when the disc is shifted from the flange and also leaving suflicient surface to close the openings of the fluid outlet ports when the cheek plate is maintained against the flange surface as shown in FIGURE 1. Spring 106 is located in the chamber 78 between the disc member 106 and a perforated retainer member 118 which is maintained by the spring against a shoulder 120 formed in the outlet chamber 78. When pressure in either fluid outlet zone is created sufiicient to overcome the resistance of spring 106, disc member 102 is shifted axially within said chamber away from the flanged outer surface of cheek plate 24 thereby opening communication between the fluid outlet ports 74 and 76 and the outlet chamber 78 through the perforated sections of the disc and retainer members. Cheek plate 24 includes :a shaft seal drain passage 123 leading to low pressure inlet port 64.

Referring to FIGURE 2, cheek plate 24 is provided with a passage 122 directly connecting fluid outlet port 74 with under-vane port 86 and provided with another passage 124 directly connecting outlet port 76 in the plate to under-vane port 88. It should be noted that by this arrangement passage 122 which connects outlet port 74 to under-vane port 86 thereby connects the fluid outlet zone 48 of pumping chamber 45 to the inner pressure etfective surfaces of those vanes passing through the fluid inlet zone 42 of pumping chamber 41 while passage 124 which connects outlet :port 76 to under-vane port 88 thereby connects fluid outlet zone 44 of pumping chamber 41 to the inner pressure efiective surfaces of those vanes passing through the fluid inlet zone 46 of pumping chamber 45.

Referring to FIGURE 3, cheek plate 22 is provided with cross-connecting passages performing the same function as passages 122 and 124 in cheek plate 24. Thus in cheek plate 22, outlet port 80 is connected by a passage 126 directly to under-vane port 87 and outlet port 81 is directly connected to under-vane port 89 by a passage 128. Passage 126 thus connects fluid outlet zone 48 of pumping chamber 45 to the inner pressure effective surfaces of those vanes passing through the fluid inlet zone 42 of pumping chamber 41 while passage 128 connects fluid outlet zone 44 of pumping chamber 41 to the inner pressure effective surfaces of those vanes passing through fluid inlet zone 46 of pumping chamber 45. Fluid outlet ports 80 and 81 of cheek plate 22 which are respectively axially opposed to and connected to fluid outlet ports 74 and 76 of cheek plate 24 are likewise temporarily closed at pump starting from connection with the fluid outlet chamber 78 by the disc member 102.

In operation, reference may be made to the schematic circuit of FIGURE 4, while presuming clockwise rotation of the rotor against cheek plate 24 shown in FIG- URE 2 and counterclockwise rotation of the rotor against cheek plate 22 shown in FIGURE 3. For the purpose of convenience, disc member 102 is represented in the schematic circuit as individual check valves each of which is indicated by the numeral 102. At starting the pump, a fluid supply from an appropriate reservoir, not shown, connected to the inlet port 58 is conducted by cored branched passages 60 and 62 to the fluid inlet ports 64 and 66 of cheek plate 24 and fluid inlet ports 68 and 69 of cheek plate 22 which respectively open to fluid inlet zone 42 of pumping chamber 41 and fluid inlet zone 46 of pumping chamber 45.

Assuming that the extreme outer ends of the vanes in pumping chamber 41 are tracking properly through the major dwell 50 of said chamber and that the outer ends of the vanes passing through the major dwell 52 of pumping chamber 45 are not tracking properly, temporarily, fluid will be displaced from fluid outlet zone 44 of :pumping chamber 41 but not from fluid outlet zone 48 of pump ing chamber 45. Fluid displacement from fluid outlet zone 44 of pumping chamber 41 is initially blocked from outlet chamber 78 by reason of valve disc member 102 closing the cheek plate 24 outlet port 76. Fluid displacement from fluid outlet zone 44 conducted to outlet port 76 and which is blocked by the disc member 102, however, is conducted by passage 124 to under-vane port 88 of cheek plate 24 which registers with all of those vane slot ports 84 of those vanes crossing over inlet ramp 36 while passing through fluid inlet zone 46 of pumping chamber 45. At the same time fluid displacement from fluid outlet zone 44 of pumping chamber 41 is conducted in cheek plate 22 -by passage 128 from the outlet port 81 to under-vane port 89 in communication with the inner pressure effective surfaces of those vanes passing through fluid inlet zone 46 of pumping chamber 45. Fluid pressure conducted to the inner ends of the vane slots acting on the inner pressure eflective surfaces 90 of the vanes urges the vanes outwardly so that the extreme outer end surfaces 30 engage the track. Such vanes continue to track properly through the major dwell 52 of pumping chamber 45; and as they cross over outlet ram-p 40 of the same chamber, fluid will be displaced from the fluid outlet zone 48.

With the vanes now tracking properly through the major dwells of both pumping chambers 41 and 45, and with fluid displacement from both fluid outlet zones 44 and 48 blocked at the outlet ports 74 and 76 by the valve disc member 102, pressure is immediately created sufficient to overcome the spring 106. Pressure acting on the inner surface 108 of the member 102 forces the same axially away from the outer surface 110 of the flange surface of cheek plate 24 and opens outlet ports 74 and 76 of said plate to the outlet chamber 78 enabling displacement from the fluid outlet zones 44 and 48 and correlated fluid outlet ports 76 and 74 to flow to housing outlet port '72.

If, at pump starting, the vanes passing through pumping chamber 41 are not tracking properly through the major dwell 50 of said chamber while the vanes passing through pumping chamber 45 are tracking properly through the major dwell 52 of such chamber, the following action will take place: fluid displacement from fluid outlet zone 48 conducted to outlet port 74 which is blocked by disc member 102 from communication with chamber 78 will be conducted by passage 122 to undervane port 86 which registers with the vane slot ports of those vanes passing through fluid inlet zone 42 while crossing over inlet ramp 42 of pumping chamber 41. At the same time fluid displacement from fluid outlet zone 48 of pumping chamber 45 is conducted in cheek plate 22 by passage 126 from outlet port 80 to undervane port 87 in communication with the inner pressure eflective surfaces of those vanes crossing over inlet ramp 34 while passing through fluid inlet zone 42 of pumping chamber 41. These vanes will be urged outwardly in engagement with the track and now with the vanes tracking properly through the major dwells of both pumping chambers, displacement from both fluid outlet zones 7 blocked at the disc member causespressure to be immediately built up at the fluid outlet ports 74 and 76 sufficient to shift the disc 102 and open ports 74 and 76 to outlet chamber 78 and outlet port 72.

When the valve disc 102 shifts to open outlet ports 74 and 76 of check plate 24 to outlet chamber '78, the fluid outlet zones 44 and 48 with their correlated outlet branch passages or .ports 76 and 74 in the cheek plate 24 and outlet ports 81 and 80 in cheek plate 22 are connected in parallel to the outlet chamber or passage 78 and to each other as in conventional pump devices of the double throw type. The outlet chamber 78 is then maintained in continuous communication with the under-vane porting of those vanes passing through both fluid inlet zones while crossing over the inlet ramps by reason of the communication of outlet chamber 78 with the fluid outlet ports of the cheek plates and the cross passages from the fluid outlet ports to the under-vane ports. In rotary vane devices of the double throw type, in order to build up system pressure which is depended upon to induce outward urging of the vanes and maintenance of the same in engagement with the track, the vanes should track simultaneously through both major dwells. Otherwise, fluid displacement from a properly operating pumping chamber is short-circuited to the inlet side of the other pumping chamber from the fluid outlet zone of said chamber past the improperly tracking vanes crossing over the major dwell of such chamber. The present invention provides an arrangement whereby if at least one vane of one pumping chamber tracks properly across the major dwell of such chamber, fluid displacement from the properly operating pumping chamber is temporarily blocked from the outlet passage and instead conducted to the inner surfaces of those vanes passing over the inlet ramp and through the fluid inlet zone of the other pumping chamber so as to urge the vanes in such chamber in engagement with the track. With the vanes tracking properly through the major dwells of both pumping chambers, the valve disc member is pressure operated out of the way and does not effect pump operation.

Although centrifugal force must still be depended upon to cause the vanes to initially move at starting of the pump, with the combination of the valve disc member and the cross-connected fluid outlet zone, fluid inlet zone under-vane porting arrangement, it is not necessary initially to have the vanes tracking across both major dwells simultaneously, a sealing condition that must exist in a conventional vane pump of the double throw type. The invention takes advantage of the probability that not all of the vanes are going to act in the same manner and that some of the vanes, perhaps only one, will track across one of the major dwells of one of the pumping chambers. When this happens, the disc, valve, and under-vane cross-connection arrangement of the invention causes the orthe-r vanes to track. This is the case whether the pump is mounted horizontally or vertically. When the pump is mounted with the rotor axis horizontal, gravity assists tracking of the vanes in the lower pumping chamber. Although gravity does not assist vane tracking through one pumping chamber when the pump is mounted with the rotor axis vertical, the impedance of gravity is not present for resisting proper tracking in the other chamber of the device.

The invention provides an arrangement which promotes pumping at lower speeds than can be attained with conventional pump devices of the double throw type. Thus, in a test under a variety of conditions of a particular rotory vane pump of the double throw type with conventional porting arrangement, inception of pumping was from 200 to 700 rpm. With the valve disc and crosspassage under-vane porting arrangement of the present invention incorporated in the same pump, inception of pumping was at 50 rpm. consistently under the same variety of conditions.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. In a pump of the type wherein the outer ends of a plurality of vanes slidably mounted in slots of a rotor telescopically mounted within a vane track successively pass through first fluid inlet and outlet pumping zones and second fluid inlet and outlet pumping zones formed between the periphery of the rotor and the vane track, said fluid inlet and outlet zones being respectively independently connected to an inlet passage and an outlet passage, each vane having a pressure effective surface oriented for urging an outer surface of said vane against the vane track, the improvement comprising: means hydraulically connected to both fluid outlet zones interrupting flow from each of the fluid outlet zones to the outlet passage and responsive pressure increases ahead of said means permitting flow to said outlet passage, and means forming a first passage and a second passage respectively independently cross-connecting the first and the second fluid outlet zones ahead of said flow interrupting means to the pressure eflective surfaces of those vanes passing through the second fluid inlet zone and to the pressure effective surfaces of those vanes passing through the first fluid inlet zone.

2. In a pump as claimed in claim 1 wherein the flow interrupting means comprises a single, shifta-bly mounted, pressure responsive valve member, resiliently biased to a position interrupting communication between both fluid outlet zones and the outlet passage.

3. In a vane type pump the combination of:

(a) A rotor rotatably mounted within a vane track having first inlet and outlet ramps and second inlet and outlet ramps to form between the rotor and the track first fluid inlet and outlet pumping zones and second fluid inlet and outlet pumping zones;

(b) A plurality of vanes slidably mounted in slots of the rotor, each vane having a pressure effective surface for urging an outer surface of said vane in engagement with the track;

(c) An inlet passage connected to the fluid inlet zones and an outlet passage connected by first and second branch outlet passages respectively to the first and the second fluid outlet zones;

((1) Valve means interrupting flow from each of said branch outlet passages to the outlet passage and responsive to pressure increases ahead of said valve means to permit flow to said outlet passage;

(e) And means forming first and second passages respectively connected to the first and the second branch outlet passages ahead of the valve means and independently cross-connected respectively to the pressure effective surfaces of those vanes passing through the second fluid inlet zone and to the pressure effective surfaces of those vanes passing through the first fluid inlet zone.

4. In a vane pump as claimed in claim 3 wherein the valve means comprises a single, slidably mounted, pressure responsive valve member resiliently biased to a position interrupting flow from each branch outlet passage to the outlet passage.

5. In a vane type pump the combination of:

(a) A rotor carrying a plurality of sliding vanes rotatably mounted within a vane track to form first fluid inlet and fluid o'utlet zones and second fluid inlet and fluid outlet zones through which the outer ends of the vanes successively pass as the rotor turns, each vane having an inner surface effective under pressure for urging an outer surface of said vane in engagement with the track;

(b) An inlet passage connected to the fluid inlet zones and an outlet passage having a first branch and a second branch respectively connected to the first and to the second fluid outlet zones;

(c) Means forming a first vane port and a second vane port in continuous open communication respectively with the pressure effective surfaces of those vanes passing through the first fluid inlet zone and the pressure effective surfaces of those vanes passing through the second fluid inlet zone;

(d) Hydraulically operated means resiliently biased to a position isolating the fluid outlet zones and the branch outlet passages from the outlet passage and with each other and responsive to pressure increases ahead of said means to permit communication therebetween;

(e) And means forming a first passage and a second passage respectively connected to the first and the second branch outiet passages ahead of said hydraulically operated means and respectively connected to the second vane port and to the first vane port.

6. In a vane pump as claimed in claim wherein the hydraulically operated means comprises a single valve disc member resiliently biased to a position closing each fluid outlet zone to its associated branch outlet passage responsive to predetermined pressure increases in either fluid outlet zone ahead of said valve disc member to simultaneously open communication between both fluid outlet zones and their respective branch outlet passages.

7. In a vane pump the combination of:

(a) A rotor carrying a plurality of sliding vanes rotatably mounted within a vane track to form first fluid inlet and outlet zones and second fluid inlet and outlet zones through which the outer ends of the vanes successively pass as the rotor turns, each vane having an inner pressure effective surface for urging an outer surface of said vane against the track;

(b) An inlet passage connected to the fluid inlet zones;

(c) A cheek plate having an inner surface maintained in fluid sealing engagement with one side of said track and the rotor and have a first and a second outlet port extending completely through the plate registering respectively with the first and the second fluid outlet zones;

(d) Means forming an outlet passage registering with the cheek plate outlet ports;

(e) Valve means between said cheek plate and said outlet passage closing each cheek plate outlet port to the outlet passage and responsive to predetermined pressure increases ahead of said valve means to open communication therebetween;

(f) And means forming a first passage and a second passage in said cheek plate cross-connecting the first and the second cheek plate outlet ports respectively to the pressure effective surfaces of those vanes passing through the second fluid inlet zone and to the pressure effective surfaces of those vanes passing through the first fluid inlet zone.

8. In a vane pump as claimed in claim 7 wherein the outlet passage includes a delivery chamber to which the cheek plate outlet ports open and said valve means comprises a single, disc member slidably mounted in said delivery chamber immediately adjacent the cheek plate and resiliently biased to a position closing said cheek plate outlet ports to said delivery chamber.

9. In a rotary vane pump having two pumping chambers each of which includes a fluid inlet zone and a fluid outlet zone, said chambers being formed between the periphery of a slotted rotor carrying a plurality of sliding vanes and the inner surface of a vane track having an inlet ramp and an outlet ramp separated by a dwell portion for each chamber, each vane having a surface effective under pressure for urging the vane in engagement with the track, said pump having an inlet passage connected to the fluid inlet zones, an outlet passage having two branches connected to the fluid outlet zones, and separate porting means of the interrupted type communicating with the pressure effective surfaces of those vanes crossing over each ramp of the track, the combination of: means forming two passages independently connected to the said branch outlet passages and the porting means of vanes crossing over the inlet ramps in a manner cross-connecting the fluid outlet zone of one of said pumping chambers to the pressure effective surfaces of those vanes passing through the fluid inlet zone of the other pumping chamber and the fluid outlet zone of the other pumping chamber to the pressure effective surfaces of those vanes passing through the fluid inlet zone of the said one first-mentioned pumping chamber; and valve means temporarily interrupting communication of the branch outlet passages with the outlet passage and each other and responsive to predetermined pressure increases ahead of said valve means for opening said communication.

10. In a pump as claimed in claim 9 wherein the valve means comprises a single, shiftably mounted, pressure responsive valve member, resiliently biased to a position interrupting communication of each fluid outlet zone and its associated branch outlet passage with the outlet passage and with each other.

11. In a rotary vane pump having two pumping chambers each of which includes a fluid inlet zone and a fluid outlet zone, said chambers being formed between the periphery of a slotted rotor carrying a plurality of sliding vanes and the inner surface of a vane track having an inlet ramp and an outlet ramp separated by a dwell portion for each chamber, each vane having a surface effective under pressure for urging the vane in engagement with the track, said pump having an inlet passage connected to the fluid inlet zones, 21 delivery chamber, a cheek plate maintained in fluid sealing engagement against one side of said track rotor and having two outlet ports extending therethrough registering with the fluid outlet zones and opening tothe delivery chamber, and separate porting means of the interrupted type communicating with the pressure effective surfaces of those vanes crossing over each ramp of the track, the com bination of: separate passage means in said cheek plate independently cross-connecting the fluid outlet zone of one pumping chamber to the porting means of those vanes crossing over the inlet ramp of the other pumping chamber, and the fluid outlet zone of the other pumping chamber to the porting means of those vanes crossing over the other inlet ramp of said one first mentioned pumping chamber; and valve means interrupting communication of each fluid outlet zone and associated cheek plate outlet port with the delivery chamber and responsive to predetermined pressure increases in said fluid outlet zones to open communication therebetween.

12. In a pump as claimed in claim 11 wherein the valve means comprises a disc member slidably mounted in the delivery chamber and resiliently biased against the cheek plate to close the two outlet ports.

13. In a pump as claimed in claim 12 wherein the disc member resiliently biased against the cheek plate serves to maintain the cheek plate in fluid sealing engagement against the track and rotor and when shifted away from said cheek plate, pressure in said delivery chamber maintains the cheek plate in said fluid sealing engagement.

References Cited by the Examiner UNITED STATES PATENTS 2,649,737 8/53 Hoen et al. 103-136 [2,755,741 7/56 Erskine 103-136 2,782,718 2/57 Pettibone 103-136 2,809,593 10/57 Klessig et a1. 103-136 2,842,064 7/58 Wahlmark 103-136 KARL J. ALBRECHT, Primary Examiner. JOSEPH H. BRANSON, IR., Examiner. 

1. IN A PUMP OF THE TYPE WHEREIN THE OUTER ENDS OF A PLURALITY OF VANES SLIDABLY MOUNTED IN SLOTS OF A ROTOR TELESCOPICALLY MOUNTED WITHIN A VANE TRACK SUCCESSIVELY PASS THROUGH FIRST FLUID INLET AND OUTLET PUMPING ZONES AND SECOND FLUID INLET AND OUTLET PUMPING ZONES FORMED BETWEEN THE PERIPHERY OF THE ROTOR AND THE VANE TRACK, SAID FLUID INLET AND OUTLET ZONES BEING RESPECTIVELY INDEPENDENTLY CONNECTED TO AN INLET PASSAGE AND AN OUTLET PASSAGE, EACH VANE HAVING A PRESSURE EFFECTIVE SURFACE ORIENTED FOR URGING AN OUTER SURFACE OF SAID VANE AGAINST THE VANE TRACK, THE IMPROVEMENT COMPRISING: MEANS HYDRUALICALLY CONNECTED TO BOTH FLUID OUTLET ZONES INTERRUPTING FLOW FROM EACH OF THE FLUID OUTLET ZONES TO THE 